Both cleanly powered and built from 2 recycled bicycles, scrap steel and wood, leaking 5 gallon water jug and a lacross stick, our pedal powered tennis ball launcher was created as a unique entry for the innovate or die pedal powered machine contest.
It allows players varying in skill levels to practice to be better at both tennis and cycling. The launcher is towed to the court on its built-in bicycle trailer. A bike is secured to it and functions to drive the device. Pedaling the cycle as one would on a trainer drives the two launcher wheels. The cyclist then aims and pulls the lever to launch balls to the hitter.

Trailer Frame:Components for the trailer frame were scavenged from an old child trailer, including the wheels, axle, and hitch that connects to the bike. The frame is constructed from 2x4's and 2x2's.

Drive Mechanism:The drive mechanism is built entirely from scrap bike parts. The bike wheel rolls on a bike hub. A chain links the hub to a sprocket welded to a bike headset, which is used as a bearing block. A drive shaft connects to the other end of the headset to transmit power to another headset bearing block with welded sprocket. A chain goes up from there to the freewheel of a 20 inch bike wheel. The chain does not wrap around the freewheel, because I needed to reverse the direction of rotation of the launcher wheel. The video below shows the details of the drive mechanism.